How will you measure 15 minutes using two hourglasses of 7 minutes and 11 minutes respectively?

Question

There are two hourglasses. The small one can measure 5 minutes and the large one can measure 7 minutes.
How can we measure 16 minutes with 2 hourglasses running together?
(If one of the hourglasses finishes leaking, then it must be flipped over immediately to keep it running. )

Answer 1

Start both hourglass at same time
As 7minutes gets competed,by 11 minutes
We remains with 4 minutes
Now as soon as 11 minutes hourglass completes ,reverse it
We get 11 minutes
Finally We get 15 minutes,4 minutes and this 11 minutes

Comments

So, after 7 min, indeed there is 4 min left in the other hourglass. Do you mean, that this will be the starting point of the measure of 15 min?

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Ya ryt.....that will be the starting point